Forbidden Legacy
by Lord Terronus
Summary: AU. All for One had a secret project: A clone. A copy of himself, loaded with additional DNA from several other heroes. When this clone is found, he is revealed to be just a teenager. With the deadliest quirk in all of history. As well as several more. What will become of this clone once he is found by the heroes? What will become of his mind?
1. Chapter 0: It Begins

**Forbidden Legacy**

 **Prologue**

Shigaraki Tomura crashed onto the floor of his hideout. His plan to kill All-Might had failed. He had lost Noumu, their ultimate weapon against the hero and he had gotten shot in the hand. All in all, he was having a really bad day.

"You were wrong, Sensei. All Might hasn't gotten weaker. Not at all!" Shigaraki cried at the glowing computer screen that read the words 'sound only'. On the other end was the most powerful villain known to man. Shigaraki's teacher. All for One.

"No, I wasn't." The distorted voice spoke. It played the voice with a pitched up and pitched down version overlaying, to create a disguised voice. Noone would know who was on the other end of the line if they weren't already familiar with them. "We simply underestimated him. It's a good thing your League of Villains came cheap. Although the loss of Noumu is significant. So much work, wasted." Sensei mused. Shigaraki chose not to ask how he knew of the fate of Noumu. Based on his knowledge of his master, it was probably a simple mind reading quirk. Sensei was full of surprises. A sudden thought emerged in Shigaraki's twisted mind.

"There was this one kid. He was about as fast as All-Might. We might've won if not for him." He explained. The kid in question was a green haired brat, who seemed all too eager to defend All-Might. Perhaps he knew that the hero was weakening as well? Or maybe he was just an easily scared child. Shigaraki hoped it was the latter.

"Oh? Were you able to get a sample, Kurogiri?" Sensei turned his attention to the warp gate user standing behind Shigaraki. He was dressed in a rather smart suit. His face was obscured by the mist that lent him his name, as was his hands. As such, noone really knew what he looked like beneath the obscuring layer. His voice came out in a low, deep tone.

"We were able to obtain a small blood sample from him and some more DNA samples from the other students." Kurogiri replied, recalling one particular kid that left some ice in his gate. Though neither of the villains could see their master, they were both certain he was grinning.

"Excellent. Send them to the lab at once. They will be most beneficial to the project." Sensei spoke in a rather pleasant voice. He then returned his attention to his apprentice.

"Do not be discouraged. This endeavor proved useful to us regardless of this setback. All we need are stronger troops." Sensei told his apprentice to calm him. Shigaraki was difficult to work with but very useful when he was focused.

"Shigaraki Tomura! You shall be known as the true symbol of terror across the globe!" He exclaimed before ending his communication. All for One rose from his seat, disconnecting his mask as he rose. He scowled at the device. His injuries in his last battle were troublesome, but not impossible to get around. In time, he would come to heal fully. In the meantime, his project needed to be checked. He passed through the secure metal door into a dark room, with only one object visible. A tube filled with a dark blue liquid, connected to a control console, on which a monitor displayed several vital signs. All for One grinned once more. The project was coming along excellently.

"My Magnum Opus. Soon you shall be ready." He mused before exiting the room, and leaving the boy sealed within. He then proceeded to exit his temporary laboratory. Kurogiri was waiting, the samples having been handed to a technician. He noticed his master appearing and opened a gate to his true lair. All for One walked into the gate with a smile on his face. Soon, everything would fall into place.

 _Two Days Later..._

"Officer Tsukauchi! We found a lead on the USJ case!" A police officer chased the Detective in question, Tsukauchi, as he was wandering to his office to continue work on his most recent case. After meeting with the U.A staff to discuss the attack on USJ, he had locked himself in his office almost all night, double checking any records available for the villainous instigators of the conflict. He turned sharply towrds his colleague, the rings under his eyes very visible.

"What is it?" He asked with his interest piqued. He hadn't gotten very far in his work so he was desperate for any possible leads to follow up on. His colleague took a moment to catch his breath before standing up to the detective with a determined expression.

"We found a building with forensic evidence of Villain operations in the vacinity. With your permission, we have pro heroes ready to move on the scene." He explained. Tsukauchi's eyes were raised in surprise. What were they doing in a lab? What connection could that have to USJ? As if reading his thoughts, the other officer continued.

"We also found some trace amounts of DNA that matched some of the U.A students." He added. That was all Tsukauchi needed. Perhaps the villains were using the DNA to create more of those multi-quirked creatures the police found near the scene.

"Send them out immediately. I'll head in ASAP." Tsukauchi replied. The officer in front of him nodded and turned around, walking away from the detective while bringing his walkie-talkie to his mouth.

"We have clearance. You may enter when ready. Please excercise caution as this is a potential villain hideout." He spoke into the device. There was a short moment of static before he received a reply.

"Don't worry, we've got this." One of the heroes replied. He recognised the voice as Mount Lady, A fairly recent pro to hit the scene. She and Kamui Woods had been sent on the scene as they were the closest heroes available. They happened to work surprisingly well together, thankfully. Hopefully they could pull through on this.

 _At the Lab..._

Kamui and Mount Lady stood in awe of the strange tube containing a nude teenager. They chose to avoid looking at them so as to not end up on some kind of watch list. But the boy's mere presence was offputting. Neither of the heroes recognised the boy from any missing person notices or wanted posters. They had surprisingly straight green hair and a muscular body. They also seemed to be not lacking in any area below the waist, but the pros swiftly diverted their attention elsewhere. The two looked to one another before moving slowly towards the control console in front of them. One button caught their attention immediately.

It read 'Eject Subject' and had a black and yellow border around it. Hesitantly, Mount Lady pushed the button. The room was illuminated in red light as the dark blue liquid contained within the tube flowed down througha vent at the bottom. Kamui Woods glared at his partner and she shrugged sheepishly in response. The alarm would be concerning if the facility wasn't eerily empty. Not a single person besides the heroes was seen in the facility.

The boy awoke collapsing into a kneeling position, one arm on the ground to stabilise himself as he coughed up the dark blue liquid he was entrenched in for... How long was it? He didn't know. He had no recollection of anything before now but flashes began playing a slideshow in his head. Images of a flaming face, a smiling old man in a cape and two crying children. Surprisingly, they both seemed to evoke an empathetic response from them. They seemed almost like...him? But neither of them seemd to look like him and some of the memory "slides" seemed to show one looking at the other. A few more people flickered through his mind as various names entered his head.

Midoriya. Todoroki. Bakugo. Kaminari. Which one, if any was his? Did he have a name? What did any of this mean? These thoughts raced through his head at high speeds as his glass chamber seemed to open. He opened his eyes and the resulting sight was blurry. It was hard to make out anything but a male and female figure stood before him. He would've asked their names but he passed out before he could. One thought stuck in his head as he collapsed.

Every one of his flashes seemed to bring to mind one word: Hero. That sounded like a good thing to be.

 **A.N: So, I was working on Black Sun Rising Chapter 2 and this idea flung itself into my head and I wrote it down. The result came from re-reading some of the manga of MHA and the Series of books by Andy Briggs. As well as a small bit of influence from Sonic Adventure 2 and Sonic Heroes. More specifically, Shadow the Hedgehog and his story. After compiling all of those things into my cauldron of ideas and stirring them with my spoon of writing, The result was Forbidden Legacy! I have a lot of ideas for this story but they should become clearer at the first chapter (This is just the prologue, after all.). In any case, feel free to Follow, Favourite, Review and all that jazz. I'll see you all later.**

 **Sincerely,**

 **Lord Terronus**

 **P.S: To the writer of** ** _Inheritence of Highest Infamy,_** **If You're reading this, PLEASE DON'T SUE ME. It's not my fault I happened to write a story about a kid with All for One conviently close to you writing a story about a kid with All for One. Well, maybe a little...**


	2. Chapter 1: Virtue from Villainy

**Forbidden Legacy**

 **Chapter 1: Virtue from Villainy**

The boy awoke in a similarly blurry environment to before, with the main difference being his surroundings. He was in a white room with blue curtains hiding him from view. To his right was some strange contraption, connected to his arm, which was sitting on a bed with blue covers. He also noticed that he seemed to have gained some clothing since he passed out, in the form of a plastic white gown covered in dots. Some memory slides flew through his mind and seemed to reveal what was going on.

He was in a hospital.

He didn't seem to recall ever being in a hospital, or even seeing one, but his scattered pieces of what he assumed was his past seemed to be certain of what this was. It was all very confusing and he would welcome anyone who could explain what the hell was going on. As if answering his silent questions, a door on the far side of the room was flung open, to reveal a smiling man with short hair and a trenchcoat. He stepped towards the boy's bed and moved the curtains, to get a better view of the boy. He reminded the man of the U.A students he met just two days prior, but no specific one came to mind. Although the scene did remind himj of his conversation with All-Might in the U.A nurse's office. He smiled down at the boy and opened his mouth to speak.

"Hi. I'm Detective Tsukauchi of the Police. I have a few questions for you, if you don't mind." He spoke in a reassuring tone. The boy hesitantly nodded, wearing a slightly perplexed expression on his face. The man pulled out a chair and sa down next to the boy's bed.

"So, What's your name?" Tsukauchi began. The boy looked more puzzled than before, as though he himself was uncertain of the answer. When he spoke, the voice that came out was quiet, almost sounding like it had been unused until now.

"I..I don't know. Midoriya? No, wait, Was it Todoroki? Or Bakugo? No, none of those sound right." The boy replied, placing a hand on his head as he thought. Tsukauchi hesitated. Those were the names of some of the U.A students he had met. The same students that matched some forensic evidence at the laboratory that was investigated earlier. How did this boy know them? His thoughts were interrupted when the boy snapped his fingers and smiled.

"I've got it! My name is Shiro Utsuro." The newly named Shiro said, slightly louder than before, suggesting a higher confidence. His voice was still quite quiet and hoarse, but it was starting to improve. Shiro didn't know where his new name came from, but the second it popped into his head, it just seemed right. Much more familiar than any of the other names swirling in his head.

"All right then. Do you remember what happened to you?" Tsukauchi asked, relieved somewhat by Shiro's newfound confidence. It would hopefully make things easier as he tried to interrogate the boy. Shiro hesitated, thinking back to what happened before passing out.

"Something about being in a glass tube. I remember having trouble breathing and seeing two people in front of me. A man and a woman, I think. It was really blurry." Shiro explained. He had the vague recollection of another person as well. A man with a scarred face and a suit, although he couldn't tell if that was real, or just a vivid dream. Tsukauchi nodded before writing something down on a clipboard he was holding. This story definitely matched what he heard back from Mount Lady and Kamui Woods, though the details were still pretty vague as to why this boy was locked up in a tube in the first place.

"I see. Do you remember anything prior to that? Any family or friends?" Tsukauchi enquired. Shiro responded almost immediately.

"Sort of, I guess? None of it seems all that familiar but I have these flashes of stuff in my head. I don't think I have a family though." Shiro revealed. The detective raised an eyebrow before adding something to his notes: ' _possible amnesia?'_

"Alright. I suppose there isn't much point in asking the rest of these questions if you can't remember anything. That's all." Tsukauchi calmly said before standing up and starting to leave. Shiro received another flash, this time more vivid than before.

 _He was staring at Alll-Might with a nervous expression. He couldn't leave now. He had so many questions to ask! A bottle hung loosely in All-Might's pocket as he began to jump._

 _"Thanks for your support!" He yelled as they took off. He seemed to have grabbed hold of All-Might's leg and was now flying far too fast for his liking. This probably wasn't the best idea in hindsight._

Shiro held his head in confusion once more. What was that? And why were all these new words circling in his head. What the hell was a Deku? What did Quirkless mean? Then something jumped out at him.

His Quirk.

He wasn't quite sure exactly what power he had but he definitely had something. If he was correct, a Quirk was some kind of superhuman power most people possessed. So what did he have? He had a few different 'memories' of what his power might be. Explosions from his hands. Ice and fire. Super strength. Electricity. All of these seemed to be ingrained in his memory but how did he use it? And how did it help him. He grew annoyed. He had hoped for answers but all that was flung his way were questions. None of it made any sense!

It was then that he noticed that something was different about his vision. Rather than the room being white, it now had a deep red tint to it. The curtains looked the same. As did his gown. He looked at where his arm was to see, not his normal hand, but a series of yellow wire like structures making the outline of his hand. He moved it slightly, whereupon some of the wires lit up for a moment. Shiro was now looking at the electrical pulses in his body. Then there was a crashing sound. Shiro turned towards the source to find a collection the wires forming the shape of a woman. On the ground was a dish that seemed to have a plate and glass on it, now shattered onto the floor. Shiro closed his eyes for a moment, then opened them to see a nurse standing in front of him, with a terrified look on her face. The walls were white once more. His normal sight had returned. The nurse rushed out of the room and slammed the door. Shiro was now even more confused. He seemed to think that was his power, but what exactly did it do?

"What was that?" He muttered to himself.

Tsukauchi looked down at the notes that he had been handed as he left the hospital. While Shiro was unconscious, a small group of doctors analysed him in order to find out things about him. One such detail the doctors were able to deduce was the boy's Quirk. The result was certainly unexpected.

The quirk the boy possessed was a familiar one. Known by those who knew of it as All For One. The ability to take the powers of others and give them powers stored in the body of the user. That was certainly unusual. Tsukauchi decided to contact the only person he knew with more specific knowledge on this. All-Might listened as he described his first encounter with the boy and the medical results over the phone. At the end, All-Might spoke up.

"That sounds suspicious. It certainly doesn't match All For One's M.O. I'll ask the U.A heroes about how we should handle this." All Might replied. He then said goodbye and hung up. He wouldn't normally do that to such a close firend, but he had a class in two minutes. He had to attend to that first. This could wait until later.

 _Meanwhile..._

Shiro looke at his arm as it glowed with a strange energy. It felt powerful but also somewhat uncomfortable. It was quite unlike the other powers he had discovered. It seemed he was capable of creating explosions in his hands, creating ice and wrapping his body in electricity, just as his memory flashes informed him. This power felt very different than any of those. It made him feel...strange. It was incredibly familiar yet quite alien. It was also the only power that he could recall the name of.

"One For All...?" He muttered to himself.

 _A few hours later..._

All Might explained the situation to Principal Nedzu as he listened patiently. This was rather concerning, but it could also prove somewhat useful. He took a sip of his tea as All Might finished describing what he had heard of the situation. He had an idea. All Might would probably dislike it, but it seemed like the best possible course of action.

"What should we do, Sensei?" All Might asked nervously. Nedzu, surprisingly, asked no questions. He simply gave an unexpected answer.

"There's only one thing we can do. Speak to this boy and invite him to U.A."

 **A.N: Wow, that took longer than I thought to write! So, some further details, including the name of our protagonist. With the help of google translate, I managed to come up with a reasonably good name. It should translate directly into "White Empty", referring to his lack of a past. The first name is partly to evoke a blank sheet of paper, where new things can be drawn upon. It's mainly just that I like the sound of it. In any case, feel free to follow, favourite, review and all that jazz and I'll see you next time!**

 **Sincerely,**

 **Lord Terronus**


	3. Chapter 2: Flashes of Fire

**Forbidden Legacy**

 **Chapter 2: Flashes of Fire**

Shiro ssat in his hospital bed, thinking. What about? Almost everything he knew, although one question sat there in his mind, taking up the most space and driving most of his thoughts. What was with his power? He only knew a few things about it: It activated mainly when he was stressed, It allowed him access to various other powers and was the most likely cause of his strange memory flashes. All of them seemed to correspond to a particular power. Using One For All brought forth images of All-Might, a school and a notebook. The other Quirks gave him similar thoughts, the school in particular coming to mind every time. It seemed to linger in the back of his head. His thoughts were interrupted by the sound of a door opening.

Toshinori Yagi looked around the hospital floor carefully. He never liked hospitals. His injuries certainly didn't help. In addition, moving around in his True Form still felt odd. He had used up as much of One For All as he could today and was stuck with looking like a sickly old man with unusual eyes. It felt so different from his Muscle form that he occasionally felt like it belonged to a different person. He walked up to the last bed with a sign on it, reading 'Shiro Utsuro'. He pulled the curtain aside and found something he certainly did _not_ expect.

Shiro was attempting to experiment with One For All when the curtains surrounding his bed were suddenly moved, revealing an old man. The very sight of him immediately brought forth many images in his head, so much so that he had to clutch his head with his other hand. Of all the new thoughts now swimming in his mind, the name of the man came up first.

"All-Might Sensei...?" He hesitantly asked. If All-Might didn't look surprised before, he certainly looked like it now. His mouth was agape at this strange boy. How did he recognize him? He quickly calmed himself and began to speak with a smile on his face.

"You're quite the perceptive kid. How did you recognize me? Does the hair give it away?" He joked. Shiro let out a laugh in response. It was an odd sound, as though it had never come out of his mouth before. He quickly stopped himself as a small white furry creature approached the two. Shiro didn't know how, but he recognised him as Principal Nedzu, the head of U.A. He wasn't really sure what that meant, but he knew it was something important.

"I honestly don't know," Shiro answered All-Might's question bluntly. "I got these strange flashes in my head that just...told me your name. It's really confusing." He concluded, muttering that last part to himself. The two standing over his bed looked at eachother and then back to Shiro.

"In that case, you're probably aware of what we are representing here-U.A high, the prestigious hero school." Nedzu said rather proudly. Shiro nodded. That was the school that kept showing up in each of his flashes. But what did they want? As if answering his unspoken question, Nedzu continued.

"We have come to understand that you possess a Quirk known as All for One. Is that correct?" Nedzu said. Shiro instantly knew he was correct, but he had no idea how he knew that. Just a few moments ago he knew next to nothing about his power and now he felt as though he fully understood it.

"Yeah. How did you know? I didn't even know that!" Shiro exclaimed, catching the two pros off guard. All-Might looked about ready to collapse-more than usual anyway- and Nedzu's eyes were as wide as they could be. He cleared his throat before speaking again.

"Welll, we would like to extend an invitation for you to join U.A. We are most interested in your situation and can provide the best possible training for you." Nedzu explained. It was now Shiro's turn to look incredibly surprised. If his eyes streched any wider, he was certain his eyeballs would fall out. It took him a few momentas befroe he could even speak again.

"Yes! Absolutely!" Shiro said. Finally, he had people he could ask about his power! People he could talk to in general. The thought of Hero Training excited him, something he noticed that seemed to be the same in his other memories. This was his chance to learn about his power!

He swore to himself on that moment not to mess it up.

"Excellent. Considering you have nowhere to stay, we have prepard a dorm room in the academy for you. We also have a uniform ready for you." Nedzu concluded. He was quite pleased with the way this went. From what All-Might had said, All For One was a very dangerous individual, but he didn't get that at all from this boy. He reminded him of his other students.

 _The Next Day..._

Shouta Aizawa walked into his classroom to find several students crowded around a new desk. They seemed to be examining it and talking amongst themselves as to who it could possibly belong to. He decided to interrupt and get started.

"If you would all stop gazing at that desk, I have an announcement to make." He spoke, causing the group to launch back into their seats so fast you would think they all had superspeed Quirks. He sighed as he placed his bandaged arms onto his desk and began to speak.

"We have a new student joining our class today. Everybody play nice. Come on in." Aizawa explained, turning to the door and waiting for the student in question to enter the class. The boy-whom Aizawa had been told was called Shiro- entered nervously, with a fearful expression on his face as he walked into the centre of the room. He shivered uncontrollably and clutched his head.

"H-hi. I'm Shiro. Shiro Utsuro. It's a pleasure to meet you all." Shiro introduced himself, bowing, partially out of respect but mostly because just looking at everyone in the room filled his head with a dozen flashes. He even recognised some of the students from his scattered thoughts. When he managed to pull himself together he looked back up, only to face a storm of questions.

"Where are you from?"

"What's your Quirk?"

How did you get into U.A anyway?"

"What do you think about capes?"

A sea of words washed over Shiro. He found himself getting rather angry. His eyes glowed a menacing red as he observed everyone, no longer as people, but rather a collection of wire like humanoid structures.

"Shut up!" He yelled, his sudden quirk activation surprising and scaring several students. At least they were quiet now. He closed his eyes, took a deep breath and composed himself.

"Sorry. My Quirk activates mostly in stressful situations." He excused as he walked over to the empty desk at the end of the class. Everyone gazed at him strangely, confused by his sudden outburst. Even Aizawa looked surprised underneath his bandages.

"Well, since we have a new student, I think that means he'll have to take the fitness test." Aizawa grinned as he spoke. The looks everyone was giving him changed from confusion to pity. They all had to take this fitness test on the first day of school. Shiro, meanwhile, looked confused. What was Aizawa on about? He didn't notice that a P.E uniform had been tossed his way until it was lying on his desk. Then his eyes widened. Another flash came and suddenly he knew what was going on.

This would be hard.

After changing into his new P.E uniform, Aizawa took Shiro out into the school yard and hiro observed the tests laid out for him. The other students came along too, dressed in their Hero costumes. They had a lesson after this involving them, but right now their focus was all on Shiro as he made his way to the first test: The 50 metre dash. Another flash gave Shiro an idea. He smirked as he moved his hands behind his back.

"Go." Aizawa said witha total lack on enthusiasm. This wasn't actually his idea, but the Principal had insisted that he should test the boy. He was surprised to see his technique match Katsuki Bakugo's, right down to the explosions. He scored 4.12 seconds, much to the surprise of everyone present.

Shiro hesitated. He had used one of his powers but he still had plenty of tricks up his sleeve. Of course, now he would have to explain his powers to the others That was a conversation he wasn't looking forward to.

 **A.N: And Scene! I think that came out pretty well. I decided to have him take the fitness test partly to show off his abilities and partly because I figured that since the school had records of everyone _but_ Shiro, They should probably make sure to have the details of everyone in the class. Just for consistency. As for the lesson hinted at, I have some plans for that next time. For now, Feel free to follow, favourite, review and all that jazz and I'll see you all next time! **

**Sincerely,**

 **Lord Terronus**


	4. Chapter 3: Tests & Terror

**Forbidden Legacy**

 **Chapter 3:** Tests & Terrors

Everyone seemed transfixed on Shiro Utsuro after his initial surprise in his Quirk Fitness Test. Seeing him mimic perfectly the performance of their fellow classmate, Katsuki Bakugou for the fifty metre sprint was certainly very surprising. Bakugou most of all, seemed surprised and irritated that his performance was so effortlessly copied.

"What the hell, you damned copycat?! How'd you do that!?" Bakugou yelled to Shiro, who turned to him, startled by the interruption.

"Sorry, Kacchan." Shiro stammered out. This only seemed to provoke the other boy more, and confuse a few others, notably one Izuku Midoriya.

"The fuck did you just call me?! You're dead, copycat!" Bakugou threatened, making menacing explosions before Aizawa put a stop to it. They didn't have the time to waste on an explanation, nor did they have the time to indulge Bakugou's ego. A single glare assured that Shiro could get on with the rest of the test.

To everyone's surprise, Bakugou was not the only one who had their strategy copied. For the grip strength test, Shiro utilised the powers of Denki Kaminari, coating his hand in electricity to overload the device. This ended up giving him the maximum possible score of 999.9 Kilograms, which was far higher than Kaminari's original result. Shiro guessed that he simply spread more electricity through his body. As it turned out, Shiro had inadvertently combined the enhancing qualities of One For All with the Electrification quirk, resulting in a far higher score.

For the long jump, Shiro mimicked the abilities of Shouto Todoroki and produced a pillar of ice which he used to travel further. For the side-stepping, Shiro went back to using his explosions, one of his personal favourite powers at this point. He considered using One For All, but he was unsure if he would be able to properly regulate that particular quirk for the events. A series of flashes proceeded to inform him that doing so was most likely beyond his capabilities.

However, he did have a plan on how to properly use it for the ball throwing event. Another flash made him aware that he could use the power of his most dangerous quirk for a rather spectacular result. It would, however, leave one of his fingers damaged, which would hinder his performance. However, based on his previous results, he assumed he had done well enough to avoid expulsion. Assuming that was still a possibility.

"Alright, take your throw." Aizawa seemed to be lacking in his usual disinterested tone as he spoke, lining up more with a tone of intense surprise. This however, paled in comparison to the reactions of the other UA students, who were all stunned to the point that Shiro was convinced their jaws would break the ground rather than stopping at falling to the floor. Despite his embarrassment, Shiro continued, proceeding to attempt to throw the ball with One For All charged in his fingertip.

Aizawa took one look at what Shiro was attempting to do and instantly realised that he had to put a stop to it. He didn't need any more than one student with results hindered by broken bones. He glared at Shiro, seeming to deactivate his quirk.

Then something else entirely happened.

Shiro's eyes went into a glowing red as the ball rocketed from his hands, this time with a strong explosion having emerged from his fingertip, instead of the sheer power of One For All. Shiro seemed to shoot a look at Aizawa that could only possibly be described as venomous, before blinking. His expression instantly softened into one of mild confusion.

"W-what just happened?" Shiro nervously asked. For a moment, he seemed to just black out. It was rather unsettling, as the last time he could recall such an occurrence happening, he woke up in a hospital. While this was comparatively much shorter, it was still concerning. Aizawa simply held out the device that showed his score, revealing a result of 576.4 metres. Shiro raised an eyebrow, as he didn't remember having taken a throw, nor did he seem to have a broken finger like he had anticipated.

Perhaps his regulation of One For All was better than he had thought?

The last few events continued in a similar fashion: Shiro would use one of his other Quirks, surprising everyone in the process and produced a rather impressive score. By the end of the test, it was very clear that he had managed to take the number 1 spot in just about every event, moving everyone else down one spot in the process.

"Unbelievable…" Was a sentiment that was seemingly echoed by everyone present. Shiro stood for a moment, unsure of how to proceed.

"I'm sure you all have questions, but I don't think I can answer most of them." Shiro spoke to the UA students, his hoarse voice cracking a little in nervousness.

"What even _is_ your Quirk?"

"Can't say."

"Why did you call Bakugou 'Kacchan'?"

"Can't say."

This seemed to continue for a few minutes; the class asked him various questions which he wasn't allowed to answer or simply didn't know how to answer. Aizawa put a stop to this after a few minutes, reminding the class that they still had another lesson to get to shortly.

"Oh, and Shiro?" Aizawa decided to speak to the enigmatic boy who appeared to be stuck in thought before his harsh words snapped him out of it. "After this, be sure to submit a costume design. We still need that from you." He reminded. Shiro tilted his head for a moment before yet another flash informed him as to what exactly Aizawa meant. Glancing around, he noticed that everyone else was already in their own costumes, while he himself was stuck in a UA Gym Uniform.

' _I should really work on controlling those. They're a little too invasive_.' Shiro made a mental note to himself.

Shiro proceeded to follow Aizawa and the rest of the class into a large indoor gymnasium for their next hero lesson. Shiro's fitness test had taken up more time than expected, but this was still a hero course. Shiro attempted to prepare himself for whatever was next.

It was at this point, that everything started to go wrong.

* * *

"Alright, we can begin your proper lessons now that that's been taken care of." Aizawa began. "As you should all know, the UA Sports Festival is fast approaching." Shiro was the only one taken aback by this news, while everyone else seemed to simply nod. Shiro thought better than to ask what the UA Sports Festival actually _was_ , hoping that he would have another memory flash to inform him. Unfortunately, it seemed that this knowledge was not in his mental archives and no such flash occurred.

"I'm sure you are also all aware that the event always ends in a one-on-one competition." Again, everyone nodded. Shiro hesitantly followed suit, pretending he understood what was happening. Given his earlier performance, he didn't seek to draw any attention to himself- or rather, any more than he already had.

"For practice, we're going to go through a series of one-on-one combat trials today. To win, you only have to get your opponent to either forfeit, or be incapacitated. Try to avoid any serious injuries. Recovery Girl has enough to worry about without another string of injured kids." Aizawa muttered that last part to himself, though Shiro managed to still pick up on it. Aizawa then proceeded to split everyone into pairs for combat. Shiro ended up facing a girl named Ochaco Uraraka.

"Nice to meet you!" She spoke in a very cheery tone of voice. Shiro smiled nervously, not particularly used to interacting with other people in general, let alone such optimistic ones.

"Likewise, I suppose. You ready?" He replied, getting into a basic fighting stance. He wasn't sure exactly how well he could do here, but he hoped he could at least land a few blows and _make them stop breathing_ -

Huh? Where did that come from? Shiro shook his head, deciding to ignore it and focus on the matter at hand. His opponent appeared to be doing the same.

"And…START!" Aizawa gave the go-ahead and Shiro charged towards Uraraka, preparing an explosion in his left hand and preparing to throw a punch with his right. Uraraka smirked and held her hands out. As soon as Shiro got close, she grabbed his sides and activated her Quirk. She proceeded to throw her opponent upwards.

Shiro grimaced. Of course, her power was Zero Gravity! A head on attack had been foolish. He attempted to steady himself with Explosion, but all he could do was keep himself from rising any higher. Just when he was about to give up, an image suddenly filled his vision.

* * *

 _He stood against the woman in a damaged city block, clearly torn apart by their clash. The woman, a maiden with dark hair and a red costume, complete with a cape stood against him, clearly scarred, with blood trailing from her wounds._

 _His face was indifferent but inside he felt some level of disgust towards the woman. How dare she oppose him, how dare she do so with_ his _power, the one he made!?He smirked, planning to end this once and for all._

" _Well, Nana Shimura, you certainly have held out longer than your predecessor, but I'm afraid I must end things here." He spoke in a calm manner, hiding his inner rage as he raised his left hand._

* * *

Everyone stopped their battles to observe Shiro and Uraraka when the latter let out a loud gasp. Upon checking, they saw that sharp black tendrils had pierced her side. This was concerning, but not overly so. A minor wound like that could be healed by Recovery Girl with relative ease.

What caught their attention was when she started to float. And rose to the ceiling.

Uraraka panicked in the air for a short while before she started to feel ill. Clearly the use of her Quirk, both on herself and Shiro, was getting to her. After a few heaves, she ended up vomiting.

This caused everyone's concerns to grow significantly. Uraraka was clearly over-exerting herself, but she showed no signs of attempting to release her Quirk.

"O-okay, you win. I-I forfeit." Uraraka weakly replied before vomiting once again. Shiro was silent, but didn't appear to stop. Looking over, everyone saw that he was now stuck halfway in the air, a hellish glare stuck on his features as his eyes glowed a deadly red.

This didn't stop even when Uraraka started to vomit blood.

"He's going too far! She's going to die!" Tenya Iida yelled out to their teacher, who was already leaping out to put a stop to this. He glared at Shiro, activating his own Quirk. Almost immediately, the tendrils retracted to Shiro's hands and both of the two students began to fall from the sky, Uraraka losing consciousness. Fortunately, Shouto Todoroki took it upon himself to assist, and carefully lowered Uraraka on a pile of ice. He chose not to show the same courtesy to Shiro, who landed unsteadily on his feet.

Shiro started to blink, holding his head. Whatever gruesome image he was forced to observe in his head left him with a splitting headache. He looked up, to see everyone staring at him in horror, and some anger mixed in.

"W-what-" Shiro began before catching sight of Uraraka.

"Oh my god. What-What did I do?" Shiro stared at his hand, now shaking. At this point the other students began to yell at him, berating his actions. Shiro couldn't hear a word they said as he stared at the blood on the floor.

"I-I Didn't- I wasn't supposed to…" Shiro struggled to produce any words. His throat felt far too dry.

What the hell did he do?

* * *

 _The black tendrils plunged into the side of Nana Shimura, and she screamed out. He was pleased as the blood began to pour from her side. But no. This was not a weapon to kill her._

 _No, he had something far worse in mind._

" _It's been a pleasure, Shimura. But it is time to end this. Forced Quirk Activation: One For All." He spoke with an almost bored tone of voice as Shimura screamed. Her body began to break, the cracks of bones and pouring of blood almost overpowering her piercing screams, which penetrated the air violently. Her eyes burst as her body slowly exploded from the inside._

 _He smiled, and turned to face an unknown audience._

" _That, is what you must do to heroes, 'Shiro'." He spoke._

* * *

"Gah!" Shiro woke in his bed, inside his UA dormitory, terrified. For a few moments, he was sure he would find the other man, the one from his nightmare, standing at the foot of his bed.

Instead, he found the sunken, yet concerned eyes of Toshinori Yagi, in his True Form. Staring at him, shaking, Shiro said only one thing.

"Who the hell is Nana Shimura?"

* * *

 **AN: And, we're back! Sorry for the rather long absence. Real life is such a pain. Combine that with working on quite a few other fanfics and concepts, and the recent death of a family member, and you have a recipe for really slow progress. I'm glad I could return, and hopefully this extra long chapter will make up for my absence. Can't wait to write more.**

 **This chapter is probably my personal favourite so far, and is part of the reason why the story is M-Rated in the first place. This story has it's dark moments and I wanted to be able to show those in full, so naturally it's a bit more mature than my usual works. This should be the most gruesome moment for a while though.**

 **Anyway, feel free to read, review, follow, favourite and all that jazz, and I'll see you next time!**

 **Sincerely,**

 **Lord Terronus**


	5. Chapter 4: Answers & Atonements

**Forbidden Legacy**

 **Chapter 4:** Answers & Atonements

Toshinori Yagi couldn't say he was particularly pleased with his new living arrangements. He would much prefer to be sitting at home, or lounging around in his agency waiting for trouble. He would even take going on patrol throughout the area over this.

However, circumstances forced him into his new living arrangements at the recently built UA dorm facility. The area was somewhat obscured from the main building, though it was only a short distance away, about five minutes off from the main campus. Apparently, the idea of dorm rooms for students and faculty had been under consideration for some time now, but currently only one student lived in them.

Toshinori's face fell. Shiro Utsuro. An exact copy of his arch nemesis, in every way. Despite understanding Nedzu's decision to allow the boy into UA, he couldn't find himself agreeing with it. It _was_ practical. This allowed them to closely monitor him, potentially allowing them to learn more about the boy's Quirk in a safe environment. His existence practically confirmed that All For One was still out there, and so learning about their greatest enemy was essential. Shiro provided the perfect way to do so.

There was also the possibility of using the copy _against_ the original. Despite the fact that he was a copy, Shiro had already shown himself to be at least capable of a separate thought process. His willingness to try and become a hero proved that much.

However, Toshinori held his doubts on that. Shiro's first day had done nothing to alleviate his concerns. His poor treatment of his classmates, his lack of control over his own Quirk and especially what had happened to young Uraraka...

"Gah!" His thoughts were interrupted by a sudden scream coming from Shiro's bedroom. He rushed over, finding Shiro sat upright in bed. The light was low, but it was clear that his face was pale as snow. He was clutching his chest tightly, seemingly trying to steady his heart. Toshinori's mouth fell open.

He never thought he would ever see All For One looking so… scared. Nor did he expect Shiro's only words;

"Who the hell is Nana Shimura?"

It was then that Toshinori realised that this was going to be a rather long night.

* * *

Shiro was panicking. He had no idea how he recognised it, but he did. Like with many things he had seen in his admittedly short life, his mind instantly processed the information as soon as the required stimuli emerged. It might have been convenient but at this moment, it terrified him.

All Might's response was much the same as his own. He could only guess that the Symbol of Peace must have held a strong connection to the name that was haunting his mind now. It clearly bothered him to hear that name from him. Come to think of it, Shiro felt that All Might was rather bothered by his entire presence. It seemed that that name coming from his mouth was in some way… _wrong_ to All Might. It only furthered his desire for answers.

"Who told you that name?" All Might asked. While he seemed to be attempting to stay calm, Shiro noticed his voice sounded a little shaken.

"I-I had a dream… Or a vision, I don't know. There was a-a man, in a suit. He said her name and…" Shiro trailed off, desperately trying to hold himself together enough to not burst into tears. All Might paused before letting out a small sigh.

"Alright, I think we need to talk. How about we get you up and we talk about this in the living room?" All Might said. The 'Living Room' was technically called the common room, but since no one but Shiro and All Might lived there, they gave it a name more fitting of a house than a dorm complex. Shiro weakly nodded and stepped out, not trusting his voice at the moment.

"Take a seat." All Might gestured towards the rather plush couch in the centre of the room. Again, Shiro shakily nodded and hesitantly sat down, attempting to calm himself.

" _Breathe."_ He tried to tell himself. _"It was just a dream..._

He wanted to believe that, he really did. But his heart told him it was real. Too real…

All Might could clearly see that despite Shiro's best efforts, he could barely hold himself together. He could only guess at what Shiro had seen. Were he more like All For One, this response would make little sense for anything related to his former master, but for a young boy?

All Might could see only one possibility. It couldn't have been anything else.

The boy had just seen death.

"You didn't answer the question." Was all Shiro had said. Fifteen minutes had passed since he had sat down, and he still could barely organise his thoughts. His mind was racing, and Shiro guessed it must have been competing with his heart, for they were seemingly neck and neck.

"No, I suppose I haven't." All Might spoke, his words carrying a solemn weight. He prepared the kettle which sat nearby, off at a shelf. A few minutes passed, neither Shiro nor All Might saying any more words, gathering their thoughts.

"Here." Shiro blinked, noticing that All Might had prepared the two of them some tea. "It'll help calm your nerves." Hesitantly, Shiro nodded, and he drank from the cup. The warm drink managed to calm him slightly, but his hands were still clearly shaking.

All Might took a seat on a chair facing Shiro, and he sighed.  
"So, what do you want to know?" All Might began. A small anger bubbled up within Shiro as he replied.

"Are you kidding?" He said his voice on edge. He stood up, panicked rage filling his voice. "I want to know who that woman was! I want to know who the man she fought was, I want to know why I _had to watch her die, I-"_

"Breathe." All Might cut off Shiro, who was now hyperventilating. Shiro sat back down, stopping himself. When he next spoke, his words came out as little more than a whimper.

"Why me?" He whispered, his eyes watering.

All Might took a long sip of his drink, and sighed at the end. His voice was filled with sorrow as he spoke.

"Nana Shimura… She was my mentor. More than that, my friend. She was the one who showed me how to smile in the face of danger, and how a hero should fight for others no matter the cost. She was the one who gave me One For All. Without her, there wouldn't be any All Might." He let out a low, bitter chuckle, a sad smile adorning his face as he remembered her.

"What…" Shiro hesitated. "What happened to her…?" Shiro asked, though certain he knew the answer.

"She died." All Might's smile was gone now. Shiro swallowed nervously.

"Do you… Do you know how?" Shiro was shaking. A part of him hoped All Might wouldn't say, or would dismiss it. He knew what he had seen, but there was no way it could have been real, right? His power couldn't do _that_ to someone…

Could it?

"I didn't see it myself. My other teacher, a man called Gran Torino, pulled me away before I could see anything. All I saw was her standing against…" All Might hesitated. He looked away from Shiro. "Against All For One."

Shiro's eyes grew wide and he gasped. "That's my Quirk's name…" He breathed. "Is that how you knew about it at the hospital? You had seen it before?" Shiro shook his head suddenly, his mind racing. "No, that doesn't add up." He muttered. All Might raised an eyebrow.

"How so?"

"With the exception of One For All, every Quirk is unique to a single person. Quirks can be passed down, but even then some differences would occur." He explained. "There's no way I could gain the exact same Quirk, and there's no reason _I_ would recognise the Quirk by name alone, _or_ why I would remember it, or any of this…" Shiro began to mutter, his ramblings reminding All Might of his successor.

"What does any of this have to do with me? How do I fit in?" Shiro said, looking straight into All Might's eyes. When All Might failed to respond for a moment, Shiro asked a more pressing question. One that had filled his mind since the moment he awoke.

"Who am I?"

All Might froze. "You still don't know, do you?" He paused. "What do you think the answer is?" Yet again, Shiro grew irritated.

"I don't know!" He screamed back, surprising All Might. "I've barely been alive for two days and already, nothing makes sense! I have the wrong memories in my head, my Quirk seems to act on its own, and I just witnessed it being used to destroy someone's body completely! How the _hell_ should I know ANYTHING! Stop dodging the question already!" Shiro's voice stopped, and when he spoke again, it was shaking. All Might noticed something he never thought he would see.

He looked again, to the face of this boy, a copy of the same person who had hunted down One For All, who had killed so many innocent people, the one who had almost killed him.

He looked, and saw tears fall from its eyes.

"Please…" Shiro pleaded. "Just tell me who I am…" He fought hard to stop himself from sobbing. All Might let out a bitter sigh.

"You are a clone. A copy of All For One."

* * *

Shiro had no idea how he was meant to respond to that information. His mind, which was almost always flowing with constant information, had finally drawn a blank on something. His once racing heart felt like it was no longer there.

"Ah…" was all that had managed to escape from his mouth. He looked down helplessly at his hands, holding them open. All Might simply watched him. Ignoring the fact that he was a copy of his worst enemy, Shiro's situation was unlike anything he had ever seen. Was there even anything he could say to comfort the boy?

Should he even _want_ to comfort him?

"I…I'm not…" All Might looked up to see Shiro looking at him, with a strangely determined look in his eyes. They were filled with water that was a hair's breath from spilling out, but in that moment, he didn't look sad.

"I'm not him." He said resolutely. The words stunned All Might for a moment.

"What?" All Might questioned, his voice shocked to a whisper. Shiro stared up at him defiantly.

"I'M _NOT_ HIM!" He yelled out. "I don't care how much of a copy I am, or what Quirk I have…" Shiro's hands balled up into fists. "I'm _nothing_ like that monster! I refuse to be!" The words were certainly strong, though All Might wasn't entirely convinced, despite the boy's conviction.

"I think young Uraraka would disagree." All Might regretted the words the moment they left his mouth. Shiro's expression morphed to one of horror for a moment. In that moment, All Might worried that he had somehow killed the boy's drive to change then and there.

But then, Shiro spoke up again.

"I'll do better." He looked up once again. Shiro still held his determined stare, looking to All Might as he continued.

"I know what I've done. I've hurt people, caused trouble… Just being here is messing everything up…" The tears in his eyes began to fall, but Shiro didn't care. He needed to say this.

"But I won't be like _him_. I won't ruin people's lives. I won't hurt anyone like him… not anymore. He's done enough. It's my turn. And this time… I'll be better!" Shiro glared at All Might, though his stare held no malice. Before All Might could respond, he turned away and walked back off to his bed. As he went to the door, he spoke once more.

"I know you hate me. You can stop trying to act nice about it. I know what I… No, what _he_ did to you." His voice held a bitter edge. "I can't say I don't deserve it. But I can say this: I'll prove you wrong. I'll prove you wrong about me." And with that, Shiro closed the door.

* * *

Toshinori stared at the space Shiro once stood in. He had no idea what to make of Shiro's words. The boy was apparently full of surprises.

He didn't think this would be the end of the problem. Not a chance. But maybe, just maybe…

He could finally see Shiro and not see All For One.

"Heh… I hope you're right kid." He muttered to himself. "I hope you _do_ prove me wrong here."

* * *

 **AN: I'M ALLLLLLLLLLLIIIIIIIIIIIIIIIIIIIIVEEEEEEEEEEEE!**

 **But seriously, I'm sorry you guys had to wait so long for this. I had actually started working on this just after Chapter 3 but… Well, life kind of got away from me. Technically, I should be studying for exams right about now, but hey, I choose Fanfiction instead. It's hard to explain, but writing this stuff really does make me feel more alive. I regret not doing this sooner. Thank you all so much for your patience, and for putting up with me for so long. Hopefully there won't be quite such a long wait for next chapter…**

 **Speaking of the chapter itself, it was originally going to be quite a bit longer, and end with Shiro back at UA. That was originally going to be where he would give his whole speech on being better, but it fit better here, and this part was such a pivotal moment that I wanted to get perfect. In the end, I simply lacked the space for anything else. I hope it's even a tenth as good as it was in my head to you, readers.**

 **That's all for now, so be sure to follow, favourite, read, review and all that jazz, and I will see you all next time!**

 **Sincerely,**

 **Lord Terronus**

 **PS: I** _ **really**_ **mean it when I say thank you to all of you. Sometimes I end up doubting myself and my work, and I get stuck in writer's block for way longer than I should, but the fact that there are people out there, enjoying my work, is all I need to keep going on my rough days. Sincerely, thank you all SO much.**


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